We were on our way to lunch and had just passed through a green light immediately east of Covenant Church when a silver sedan pulled out of the church parking lot (the green flag on the map below). No one was immediately bearing down on the fast lane, so we expected them to accelerate up to the speed of regular traffic and stay in that line. Instead they drifted into the center lane, cutting us off, into the right lane and then back to straddle the two lanes. Vogon was annoyed and makes a snarky comment about the quality of their driving.
Where Trinity Mills splits to become the frontage road along the GWB Turnpike, the car began to weave erratically, affecting other drivers around us. They pulled up to the light at Kelly behind a truck in the left lane and made a sudden lane change to be first at the light in the center lane. Then, while there is cross traffic with the light in its favor, the car began advancing into the intersection (indicated by the right/easternmost warning sign on the map). At that point we were convinced the driver is under the influence of something and decide to report this to the police.
I'm used to Colorado's Star-CSP program  and don't know the Texas equivalent , so Vogon suggested I dial 411 and get connected to the Carrollton police. While waiting to be put through to the police, the car clipped the curb just west of the light at Scott Mill (the center warning sign on the map). A dispatcher picked up and I gave her my location only to find I've been put through to the Highland Park Police (a community ~15 miles south of us) and they put me through to the Carrollton Police as the car clipped the curb again, this time narrowly avoiding hitting the sound wall alongside the road (the left/westernmost warning sign on the map).
We lost sight of the car as it went straight at Josey (the red flag on the map) and we turned to get to our destination, but we were able to tell the police the make/model and license plate number of the car. I hope that was enough to prevent an accident.
1. The Colorado State Patrol can be reached from a cellular phone within the state by dialing Star-CSP (*277); dispatchers determine whether the call requires immediate assistance or can be referred to a computerized system for lodging complaints about aggressive drivers. Suspected drunk drivers can be reported by dialing Star-DUI (*384).
2. A little Google juice turned up the TXDOT Motorists Helpline, 1-800-525-5555, to request assistance when "your vehicle is disabled or you are stranded on the side of the road [or] you want to report a drunk driver."